#ifndef THREADS_THREAD_H
#define THREADS_THREAD_H

#include <debug.h>
#include <list.h>
#include <hash.h>
#include <stdint.h>
#include "threads/synch.h"
#include "filesys/file.h"
#include "vm/mmap.h"

/* States in a thread's life cycle. */
enum thread_status
  {
    THREAD_RUNNING,     /* Running thread. */
    THREAD_READY,       /* Not running but ready to run. */
    THREAD_BLOCKED,     /* Waiting for an event to trigger. */
    THREAD_DYING        /* About to be destroyed. */
  };

/* Thread identifier type.
   You can redefine this to whatever type you like. */
typedef int tid_t;
#define TID_ERROR ((tid_t) -1)          /* Error value for tid_t. */

/* Thread priorities. */
#define PRI_MIN 0                       /* Lowest priority. */
#define PRI_DEFAULT 31                  /* Default priority. */
#define PRI_MAX 63                      /* Highest priority. */

/* Thread nice values */
#define NICE_MIN -20
#define NICE_DEFAULT 0
#define NICE_MAX 20

#ifdef USERPROG
#define RET_STATUS_INIT 0
#define RET_STATUS_ERROR -1
#endif

/* Recent CPU default value */
#define RECENT_CPU_DEFAULT 0

/* A kernel thread or user process.

   Each thread structure is stored in its own 4 kB page.  The
   thread structure itself sits at the very bottom of the page
   (at offset 0).  The rest of the page is reserved for the
   thread's kernel stack, which grows downward from the top of
   the page (at offset 4 kB).  Here's an illustration:

        4 kB +---------------------------------+
             |          kernel stack           |
             |                |                |
             |                |                |
             |                V                |
             |         grows downward          |
             |                                 |
             |                                 |
             |                                 |
             |                                 |
             |                                 |
             |                                 |
             |                                 |
             |                                 |
             +---------------------------------+
             |              magic              |
             |                :                |
             |                :                |
             |               name              |
             |              status             |
        0 kB +---------------------------------+

   The upshot of this is twofold:

      1. First, `struct thread' must not be allowed to grow too
         big.  If it does, then there will not be enough room for
         the kernel stack.  Our base `struct thread' is only a
         few bytes in size.  It probably should stay well under 1
         kB.

      2. Second, kernel stacks must not be allowed to grow too
         large.  If a stack overflows, it will corrupt the thread
         state.  Thus, kernel functions should not allocate large
         structures or arrays as non-static local variables.  Use
         dynamic allocation with malloc() or palloc_get_page()
         instead.

   The first symptom of either of these problems will probably be
   an assertion failure in thread_current(), which checks that
   the `magic' member of the running thread's `struct thread' is
   set to THREAD_MAGIC.  Stack overflow will normally change this
   value, triggering the assertion. */
/* The `elem' member has a dual purpose.  It can be an element in
   the run queue (thread.c), or it can be an element in a
   semaphore wait list (synch.c).  It can be used these two ways
   only because they are mutually exclusive: only a thread in the
   ready state is on the run queue, whereas only a thread in the
   blocked state is on a semaphore wait list. */
struct thread
  {
    /* Owned by thread.c. */
    tid_t tid;                          /* Thread identifier. */
    enum thread_status status;          /* Thread state. */
    char name[16];                      /* Name (for debugging purposes). */
    uint8_t *stack;                     /* Saved stack pointer. */
    int priority;                       /* Priority. */
    struct list_elem allelem;           /* List element for all threads list. */

    /* Shared between thread.c and synch.c. */
    struct list_elem elem;              /* List element. */

    int base_priority;                  /* Base priority of a thread. */ 
    bool donated;                       /* If a thread has donated priority. */
    struct list locks;                  /* List of locks hold by a thread */
    struct lock *blocked;               /* The lock blocking the thread */

    int nice;
    //每一个线程都有一个用来记录对于其他线程的友好程度的nice整型变量，其范围为-20到20，nice为0时对其他线程没有影响。当nice为正数时，其值越大，越会降低该线程的优先级从而让出CPU时间；当nice为负数时，其值越小，越会从其他线程中获取CPU时间。nice初始化为0，线程创建时，从父线程那里继承nice值。
    int32_t recent_cpu;                 
    //recent_cpu记录了一个线程最近的CPU使用情况，在函数thread_get_recent_cpu()中完善，如果一个线程最近都没有使用过CPU时间，它会被设为0，这样可以有效地防止线程饥饿的产生

    unsigned magic;                     /* Detects stack overflow. */

#ifdef USERPROG
    /* Owned by userprog/process.c. */
    uint32_t *pagedir;                  //Page directory. 
    struct semaphore sema_wait;         //Semaphore for process_wait. 
    struct semaphore sema_exit;         //Semaphore for process_exit. 
    struct thread *parent;              //The parent of the thread 
    struct file *exec;                  //The file containing the thread executable 
    struct list files;                  //A list of open files 
    struct list mfiles;                 //A list of memory mapped files 
    struct list children;               //A list of children process 
    struct list_elem child_elem;        //List elem for children list 
    int ret_status;                     //Return status. 
    bool exited;                        //If the process exited? 
    bool waited;                        //If parent thread has called 
#endif
    
  };

/* If false (default), use round-robin scheduler.
   If true, use multi-level feedback queue scheduler.
   Controlled by kernel command-line option "-o mlfqs". */
extern bool thread_mlfqs;

void thread_init (void);
void thread_start (void);

void thread_tick (void);
void thread_print_stats (void);

typedef void thread_func (void *aux);
tid_t thread_create (const char *name, int priority, thread_func *, void *);

/* Uses numeric less than on priority to compare two 
   elements of the ready threads list */
bool lessPriority (const struct list_elem *a, const struct list_elem *b,
                         void *aux UNUSED);

void thread_block (void);
void thread_unblock (struct thread *);

struct thread *thread_current (void);
tid_t thread_tid (void);
struct thread *thread_by_tid (tid_t);
const char *thread_name (void);

void thread_exit (void) NO_RETURN;
void thread_yield (void);

/* Performs some operation on thread t, given auxiliary data AUX. */
typedef void thread_action_func (struct thread *t, void *aux);
void thread_foreach (thread_action_func *, void *);

int thread_get_priority (void);
void thread_set_priority (int);
void thread_set_priority_extra (struct thread *, int , bool );

int thread_get_nice (void);
void thread_set_nice (int);
int thread_get_recent_cpu (void);
int thread_get_load_avg (void);

void thread_calculate_load_avg (void);
void thread_calculate_recent_cpu (struct thread *t, void *aux UNUSED);

#endif /* threads/thread.h */
